An internal combustion engine (hereinafter, abbreviated as “engine”) of an automobile or the like is configured such that combustible air-fuel mixture is formed by mixing fuel injected from a fuel injection device and air introduced into the engine through a suction pipe, and the combustible air-fuel mixture is burnt in a cylinder. It has been known that, in such an engine, a mixture state of fuel injected from the fuel injection device and air largely influences performance of the engine. Particularly, it has been known that atomization of fuel injected from the fuel injection device is an important factor which influences performance of the engine.
FIG. 54 illustrates views showing a nozzle plate 1002 mounted in a fuel injection port 1001 of a fuel injection device 1000. The nozzle plate 1002 is formed such that a nozzle hole 1003 having a quadrangular shape as viewed in a plan view gradually increases a size thereof toward the other end side from one end side in the plate thickness direction, and is mounted in the fuel injection port 1001 of the fuel injection device 1000 such that one end side of the nozzle plate 1002 in the plate thickness direction is positioned on a fuel injection port 1001 side of the fuel injection device 1000. An interference body 1005 is formed on a nozzle hole opening edge 1004 on the other end side of the nozzle plate 1002 in the plate thickness direction, and the interference body 1005 is configured to partially close the nozzle hole 1003.
In the fuel injection device 1000 provided with such a nozzle plate 1002, when fuel flows out from the fuel injection port 1001, atomized fuel F2 which impinges on the interference body 1005 and flows along a surface 1008 of the interference body 1005 impinges on fuel F1 which flows along an inner wall surface 1006 of the nozzle hole 1003 so that fuels F1 and F2 are atomized and are injected into the inside of a suction pipe from the nozzle hole 1003 (see JP-A-10-122097).
However, in the nozzle plate 1002 shown in FIG. 54, an inlet-side nozzle hole portion 1003a positioned on a fuel injection port 1001 side of the fuel injection device 1000 and an outlet-side nozzle hole portion 1003h positioned downstream of the inlet-side nozzle hole portion 1003a along the fuel injection direction are formed by etching, and respective corner portions 1007 of the outlet-side nozzle hole portion 1003b are rounded. As a result, fuel injected from the nozzle hole 1003 formed in the nozzle plate 1002 minimally forms a sharpened liquid film and hence, atomization generated by friction of fuel with air becomes insufficient.